In recent years, as a method of measuring an abdominal fat such as a visceral fat and a subcutaneous fat, a method of using bioelectrical impedance information and physical information of a user is examined. With this method, the bioelectrical impedance is measured with using electrodes in contact with a trunk or the like of the user, and a circumferential length, vertical width, horizontal width, and the like of the trunk are measured as the physical information.
For example, patent document 1 proposes a visceral fat measuring device in which an electrode support portion for supporting an electrode for measuring the bioelectrical impedance and a pair of arm portions to be brought into contact with both sides of an abdominal part so as to measure the horizontal width of the trunk are integrally formed.
However, with this device, since the information measured as the physical information of the user is only the horizontal width of the trunk, there is a problem that reliability is insufficient for precision of the physical information. That is, the abdominal part and a periphery thereof of the trunk of a human being is a part where a shape is easily changed by a breathing action. A section of the abdominal part is changed so that at the time of inhalation, the vertical width is extended and the horizontal width is contracted, and at the time of exhalation, the vertical width is contracted and the horizontal width is extended. Thus, measurement values are differentiated between a case where the horizontal width of the trunk is measured upon the inhalation and a case where the horizontal width is measured upon the exhalation, so that calculation of indicators relating to a body fat is varied.
Therefore, it can be said that as the physical information, the vertical width and the horizontal width of the trunk are preferably measured at the same time, so that a breathing state is reflected. Thus, in the above device, when an arm portion for measuring the vertical width of the trunk is newly provided, there is a need for also providing an encoder for measuring a moving distance of the arm portion. However, since the encoder is a highly expensive part, production cost is increased. According to an increase in the number of parts, probability of failure is increased, so that there is an anxiety that maintenance cost is increased.